1. Field of the Invention
The present invention relates to planar optical devices and particularly to an alignment system for aligning active devices with planar, passive optical devices.
2. Technical Background
Optical networks used in the communications industry require many complex optical components, examples of which include NXM switches, gain-flattening filters, variable attenuators, and add-drop multiplexers. An efficient way to design such components is to use planar optical devices inasmuch as many optical functions can be implemented on the same substrate. Furthermore, active devices can be added to the planar platform in order to create hybrid components delivering many of the functions needed in optical networks in a relatively compact package used for switching, monitoring, wavelength multiplexing, demultiplexing, wavelength conversion, and the like.
One difficulty with manufacturing hybrid devices is the precise alignment of active devices such as semi-conductor lasers, photo diodes and the like with the passive devices, such as waveguides, couplers, and switches on the same substrate. In the past, active alignment has been employed where the optical performance of a hybrid component is monitored as the active device is physically moved into alignment until, for example, a semi-conductor laser is aligned with a passive silica waveguide. The output from the waveguide is monitored until its optimal output is detected and, at such time, the active device is affixed, such as by soldering, to the platform of the passive device. This method is extremely time consuming and requires a complex experimental set-up to perform such alignment.
Another method employed in the prior art is the use of alignment marks on, for example, an optical waveguide substrate and separate alignment marks on an active platform and the subsequent alignment of the respective alignment marks to one another when the active device platform is joined with the passive device platform. This too requires precise placement of alignment marks initially on both platforms and the subsequent precise alignment of the active and passive platforms during their joining and bonding.
There exists a need, therefore, for a system and resultant hybrid component in which an active device can be precisely aligned to a planar optical component of a passive platform such that the active device is precisely coupled to the component. As hybrid optical components become increasingly in demand and the number of optical functions implemented on a single wafer increases, so too does the need to realize efficient and precise alignment of passive and active optical devices.
The method and resultant structure of the present invention provides such precise alignment of hybrid components by forming alignment standoff elements on a passive platform which matingly receive the mirror image structure of an active platform containing, for example, an active element to be aligned a waveguide of the passive platform. The two platforms precisely self-align with one another without the need for experimental positioning of the active device with respect to the passive device or the utilization of indexing marks in an effort to align the passive and active platforms. The method of forming a hybrid device according to the present invention includes the steps of masking and etching on a core layer of a planar optical component to define at least one standoff alignment element and an optical element and subsequently overcladding the optical element such that a passive platform is formed which exposes an optical element such as a waveguide and standoff alignment element for receiving a mirror image alignment element of an active platform including an active device, such as a solid state laser.
Hybrid components embodying the present invention include a passive platform having at least one standoff alignment element and an optical component formed therein for receiving an active platform with a mating mirror image alignment element. Such a fabrication method and resulting optical component provide a highly efficient, self-aligning passive and active component platforms which greatly reduce the cost of fabrication of hybrid optical components as well as improve their reliability and reduce their cost.
Additional features and advantages of the invention will be set forth in the detailed description which follows and will be apparent to those skilled in the art from the description or recognized by practicing the invention as described in the description which follows together with the claims and appended drawings.
It is to be understood that the foregoing description is exemplary of the invention only and is intended to provide an overview for the understanding of the nature and character of the invention as it is defined by the claims. The accompanying drawings are included to provide a further understanding of the invention and are incorporated and constitute part of this specification. The drawings illustrate various features and embodiments of the invention which, together with their description serve to explain the principals and operation of the invention.